Project Summary The long-term goal of this dissertation research study is to help public and private payers build their own budget impact models, to better inform their formulary decisions, and ultimately maximize efficiency in their health care systems. We will achieve this goal by collaborating with the national TRICARE payer, which serves the military and their dependents, to develop a budget impact model for their recent formulary changes. The objective of this study is to evaluate the budget impact of TRICARE?s recent antidiabetic drug formulary changes. The specific aims of the project are: i) develop a model to predict the budgetary impact of TRICARE?s antidiabetic drug formulary changes, ii) calculate the actual empirical budget impact one year after implementation of the formulary changes, and iii) identify, compare, and contrast the cost drivers in the budget impact model versus empirical analysis. Both the budget impact model and empirical analysis will use existing TRICARE pharmacy and medical claims data. To successfully conduct this research, the principal investigator will attend International Society for Pharmacoeconomics and Outcomes Research short-course programs in topics such as budget impact analyses, modeling, advanced decision modeling, and statistical methods in economic evaluations, as well as University of Maryland, Baltimore professional development workshops and responsible conduct of research courses. The principal investigator will also learn stakeholder engagement as a project manager in the PATIENTS Program. Additionally, the principal investigator will have biweekly 1-on-1 meetings and biweekly team meetings with the sponsor-- University of Maryland, Baltimore?s Professor Mullins, who has expertise in budget impact analyses and payer engagement, and will reinforce principles. In addition to the sponsor, four other experts in TRICARE, clinical diabetes treatment and management, decision analyses, and large databases will serve on the principal investigator?s dissertation committee and provide guidance.